1. Field of the Invention
The present invention relates to a gas turbine engine, and more specifically to cooling of the turbine blades in the turbine section of the engine.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
Gas turbine engines include stationary vanes and rotating blades in the turbine section that have cooling fluid passages therein. The cooling fluid is usually air, and the supply for cooling air is usually from the compressor of the gas turbine engine. The first, second, and third stage turbine blades are usually cooled by air supplied from the compressor at various pressures. The cooling air is exhausted to the gas stream from cooling holes in the blades. The first stage blade operates under higher pressures, and therefore requires a cooling fluid supply having such a pressure that the flow can be exhausted into the gas stream. The second and third stage blades also require compressed cooling air in order to exhaust the cooling air into the gas stream. The last stage blade operates under the lowest gas stream pressure, and therefore requires the lowest cooling air pressure of all the stages. Using compressed air supplied from the compressor for the last stage blades waists compressed air and decreases the overall efficiency of the turbine engine.
What is needed is a way to improve the efficiency of the gas turbine engine without requiring as much cooling air from the compressor.
The object of the present invention is to provide for cooling of the last stage blade in a gas turbine engine while also reducing the amount of cooling air bled off from the compressor in order to improve the performance of the gas turbine engine.
The object of the present invention is to reduce the need for cooling air supplied from the compressor and therefore increase the efficiency of the gas turbine engine.
Another object of the present invention is to use the rotation of the fourth stage blade as a pumping means to drive a cooling air from the atmosphere surrounding the turbine through the fourth stage blade for cooling thereof.